Digital printing method and printing device having a cup-shaped printing carrier

ABSTRACT

In a method and device to print a carrier material, a print carrier is provided with depressions on a surface. On the surface, a fluid layer is applied such that the depressions are filled with fluid. In a structuring process, ink-attracting and ink-repelling regions are generated so that the fluid in the depressions is removed in the ink-attracting regions not removed in the ink-repelling regions. Ink that adheres in the ink-attracting regions and which does not adhere in the ink-repelling regions is applied on the surface. The ink applied on the surface of the print carrier is transferred to the carrier material.

BACKGROUND

In a method and a device to print a carrier material, a print carrierhas a plurality of depressions on its surface. Such a print carrier is,for example, known from the rotogravure technique.

Digitally operating print methods have been known in which a structuringin ink-attracting and ink-repelling regions is effected via digitallycontrolled energy sources, for example lasers. Before the restructuringof the same surface of the print carrier, the respective surface is tobe cleaned precisely. For this, corresponding cleaning stations arenecessary that increase the hardware expenditure.

For example, from U.S. Pat. No. 5,067,404 a digitally-operating printmethod is known in which a fountain solution is applied to the surfaceof the print carrier. The fountain solution is vaporized via selectiveapplication of radiant energy in image regions. The water-free regionslater form the ink-bearing regions that are directed to a developingunit and are inked by means of an ink vapor. After the transferprinting, the ink residues must be completely removed from the surfaceof the print carrier in order to reapply a fountain solution and torestructure this.

Furthermore, from U.S. Pat. No. 6,295,928 (corresponding to WO98/32608), a method is known in which an ice film is applied to thesurface of the print carrier and this ice film is structured with theaid of local thermal energy, whereby, for example, adigitally-controlled laser system is used. After the transfer printing,the ice layer and the ink residues must be removed in order to enable arestructuring with new print images.

From DE-A-101 32 204 (not published) by the same applicant, a CTP method(Computer-To-Press method) is specified whereby multiple structuringprocesses can be implemented on the same surface of the print carrier.The structuring into ink-attracting and ink-repelling regions iseffected with the aid of digitally-controlled systems, for example lasersystems. The ink-attracting regions are later inked with ink. Thesurface of the print carrier is cleaned before a new structuringprocess.

Cleaning devices that can be used for digitally-operating print methodsare, for example, specified in DE-A-100 63 987 by the same applicant.For cleaning, the surface of the print carrier is charged with cleaningfluid, whereby further measures (such as the use of ultrasound energy)can be added.

From WO 01/02170 A by the same applicant, a method and a print device toprint a carrier material and to clean a printing roller are known. Theprint carrier comprises a plurality of depressions in which ink can beaccepted. In a structuring process, this ink in the depressions ischarged with a thermal energy, whereby ink-printing regions and regionsthat emit no ink are generated. The surface of the print carrier iscompletely cleaned with the aid of a complex cleaning station before arestructuring.

DE 102 08 250 A1 (not published) specifies a printing method in whichthe surface of a print carrier is wetted with a fountain solution. Withthe aid of energy, the fountain solution is removed at image locations,the surface is inked and the ink is transferred to an intermediatecarrier, for example a rubber blanket band. From there, the ink istransferred to a carrier material. The surface of the print carrier isrespectively cleaned between two print cycles.

DE 195 03 951 C2 and EP 0 711 671 A1 are referenced as further priorart.

SUMMARY

It is an object of the invention to specify a printing method and aprint device that permits different print images to be generated on thesame surface of the print carrier, whereby the cleaning expenditure isminimized.

In a method and device to print a carrier material, the print carrier isprovided with depressions on a surface of the print carrier. On thesurface of the print carrier, a thin, homogenous fluid layer is appliedsuch that the depressions fill with fluid. In a structuring process,ink-attracting and ink-repelling regions are generated so that the fluidin the depressions is removed in the ink-attracting regions and thefluid is not removed in the ink-repelling regions. Ink that adheres inthe ink-attracting regions and does not adhere in the ink-repellingregions is applied on the surface. The ink applied on the surface of theprint carrier is transferred to the carrier material. A fluid layer isreapplied on the same surface of the print carrier and the print processis continued.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a print device for printing a carrier material.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the preferred embodimentillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, such alterations andfurther modifications in the illustrated device, and/or method, and suchfurther applications of the principles of the invention as illustratedtherein being contemplated as would normally occur now or in the futureto one skilled in the art to which the invention relates.

In a method to print a carrier material, a print carrier has a pluralityof depressions on its surface. On the surface of the print carrier, athin, homogenous fluid layer is applied, such that all depressions fillwith fluid. In a structuring process, ink-attracting and ink-repellingregions are generated, whereby the fluid is removed in the depressionsin ink-attracting regions and in ink-repelling regions the fluid is notremoved. Ink that adheres in ink-attracting regions and does not adherein ink-repelling regions is applied to the surface. The ink applied onthe surface of the print carrier is, in the further course, directlytransferred to the carrier material. A fluid layer is reapplied on thesame surface of the print carrier and the print process is continued.

All depressions that in general have a cup shape are filled with fluid,for example water. In a subsequent structuring process that is generallydigitally controlled, the fluid in the depressions in ink-attractingregions is removed, for example via vaporization. The fluid is stillpresent in the depressions in the ink-repelling regions. The totalusable surface of the print carrier is then inked with ink that isrepelled by the fluid, but however is accepted by the depressionswithout fluid. The carrier material, for example paper, now comes intodirect contact with the surface. The ink is thereby completelytransferred from the depressions to the carrier material. After thetransfer printing, all depressions are empty and also contain no inkresidues. Consequently, the thin, homogenous fluid layer can immediatelybe applied again in the next process step and a restructuring intoink-repelling and ink-attracting regions can occur. A cleaning betweentwo print cycles is thus foregone, whereby a corresponding cleaningstation can be omitted. The hardware expenditure for the realization ofthe method is thus reduced. It can be possible that a cleaning isnecessary in a simplified form after large temporal intervals. However,in general such a cleaning is not necessary between two successive printcycles, but rather only after a large number of print cycles and alsothen only in a simplified form of the cleaning, such that the cleaningexpenditure is then also reduced. High printing speeds can consequentlybe achieved given application of a digital printing method.

In FIG. 1, a print device is shown via which the specified method forprinting of a carrier material can be realized. A print carrier 10, alsodesignated as a form cylinder, has a surface structure that is shownenlarged in image section 12. The surface structure comprises cups 14arranged two-dimensionally in a grid, for example in a grid of 300 toapproximately 2500 dpi (dots per inch), preferably 600 to 1200 dpi.Corresponding image points can be printed with the aid of these cups.The cup is depth 0.1 to 50 μm, preferably 5 to 20 μm.

A dampening system 16, an image generation device 18, an inking system20 and a counter-pressure cylinder 22 (also called an “impressionroller”) are arranged around the circumference of the cylindrical printcarrier 10. The carrier material 24 is conducted through between thecylindrical print carrier 10 and the counter-pressure cylinder 22. Itpasses through a drying station 26 for drying.

Given rotation of the print carrier 10 in the arrow direction P1, theapplication of a thin, homogenous fluid layer occurs on the dampeningsystem 16, such that all cups 14 fill with fluid, preferably water. Thefountain solution application occurs, for example, via rollers, howeverthe application can also alternatively occurs via spraying or vapordeposition.

Excess fountain solution is preferably removed with a scraper (notshown) which is downstream from the dampening system 16. The fountainsolution is selectively vaporized via a digitally-operating imagegeneration device 18, whereby ink-attracting and ink-repelling regionsare generated. In the ink-attracting regions, the fluid in the cups 14is removed; in the ink-repelling regions, the fountain solution is notremoved. The image generation device 18 can, for example, be adigitally-controlled laser or a differently-controlled energy source.Via the inking system 20, ink that adheres to the surface of the printcarrier 10 in the ink-attracting regions and does not adhere in theink-repelling regions is applied on the surface of the print carrier 10.Given use of a water-containing fountain solution, the ink is generallyoil-containing. Excess ink is removed via a scraper (not shown)downstream from the inking system 20.

The printing ink is subsequently directly transfer printed to thecarrier material 24. The transfer onto the elastic intermediate carrieras specified in the patent document U.S. Pat. No. 5,295,928 is omitted.The ink transfer is effected via adhesion forces. Via correspondingexecution of the printing ink with regard to its viscosity andcross-linkage, as this is known, and via suitable design of the cupshape, one achieves a very good emptying of the cups 14. Printing inksbased on water, as this is used in known rotogravure methods, arepreferred given use of print carriers with relatively large cup depthsand their problem of complete emptying.

The carrier material is subsequently directed through a drying station26 that dries the ink.

As mentioned, a fountain solution that comprises water is preferablyused. Wetting-aiding substances, for example surfactant, can then beadded to the fountain solution. Alternatively, silicon-repelling fluidscan also be used in order to process silicon-containing printing inks.

In the region of the transfer printing location, an electrostatic fieldcan be applied in order to support the emptying of the ink from the cups14 in the surface of the print carrier 10.

As mentioned, no cleaning station is arranged between the transferprinting and the reapplication of fountain solution. The cups 14 arecompletely emptied. After a reapplication of fountain solution, astructuring in ink-attracting and ink-repelling regions can occur,either corresponding to the previous print image or corresponding to anew print image. In this manner, print images of smaller and largereditions can be printed with the same print carrier with highflexibility. Due to the omission of the cleaning process, which can benecessary only in simplified form and at substantially larger temporalintervals, an increased print speed can be achieved relative to theprevious digital printing method.

While a preferred embodiment has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that only the preferred embodiment has been shown anddescribed and that all changes and modifications that come within thespirit of the invention both now or in the future are desired to beprotected.

1-19. (canceled)
 20. A method to print a carrier material, comprisingthe steps of: providing a print carrier with a plurality of depressionson a surface of the print carrier; applying on the surface of the printcarrier a thin, homogenous fluid layer such that all of the plurality ofdepressions fill with fluid; in a structuring process, generatingink-attracting and ink-repelling regions so that the fluid in thedepressions is removed in ink-attracting regions and the fluid is notremoved in the ink-repelling regions; applying on the surface ink thatadheres in the ink-attracting regions and does not adhere in theink-repelling regions; directly transferring to the carrier material theink applied on the surface of the print carrier; and reapplying a fluidlayer on the same surface of the print carrier and continuing the printprocess, a plurality of print cycles following one another occurringwithout the surface of the print carrier being cleaned.
 21. A methodaccording to claim 20 wherein the depressions form a cup structure witha cup depth in a range of 0.1 to 50 μm.
 22. A method according to claim20 wherein the cups are arranged in a grid of 300 to 2500 dpi, on ausable surface of the print carrier.
 23. A method according to claim 20wherein the fluid comprises water.
 24. A method according to claim 23wherein wetting-aiding substances are added to the water-containingfluid.
 25. A method according to claim 20 wherein the fluid comprisessilicon-repelling substances and the ink comprises silicon-containingsubstances.
 26. A method according to claim 20 wherein excess fluid isremoved by a scraper after application of the fluid.
 27. A methodaccording to claim 20 wherein excess ink is removed with aid of ascraper after the application of the ink.
 28. A method according toclaim 20 wherein in a region of the transfer printing location, anelectrostatic field is effective that supports emptying of the ink fromthe depressions in the surface of the print carrier.
 29. A methodaccording to claim 20 wherein the printed carrier material is dried. 30.A method according to claim 20 wherein the print carrier is one ofcylindrical and disc-shaped.
 31. A device to print a carrier material,comprising: a print carrier having a surface and a plurality ofdepressions therein; an applicator which applies a thin, homogenousfluid layer on the surface such that all of the plurality of depressionsare filled with fluid; an image generator which generates ink-attractingand ink-repelling regions in a structuring process whereby the fluid inthe depressions is removed in the ink-attracting regions and the fluidis not substantially removed in the ink-repelling regions; an inkapplying station where ink that adheres in the ink-attracting regions onthe surface of the print carrier and does not adhere in ink-repellingregions is applied to the surface of the print carrier; an ink transferprinting station where ink applied on the surface of the ink carrier isdirectly transferred to the carrier material; the applicator reapplies afluid layer on the same surface of the print carrier after the inktransfer; and a plurality of print cycles follow one another without thesurface of the print carrier being cleaned; and at the ink transferprinting station an electrostatic field generator that supports theemptying of the ink from the depressions in the surface of the printcarrier.
 32. A device according to claim 31 in which the depressionsform a cup structure with a cup depth in a range of 0.1 to 50 μm.
 33. Adevice according to claim 31 in which the cups are arranged in a grid of300 to 2500 dpi on the usable surface of the print carrier.
 34. A deviceaccording to claim 31 in which the fluid comprises water.
 35. A deviceaccording to claim 34 in which wetting-aiding substances are added tothe water-containing fluid.
 36. A device according to claim 31 whereinthe fluid comprises silicon-repelling substances and the ink comprisessilicon-containing substances.
 37. A device according to claim 31wherein the printed carrier material is dried.
 38. A device according toclaim 31 wherein the print carrier is one of cylindrical anddisc-shaped.
 39. A method to print a carrier material, comprising thesteps of: providing a print carrier with depressions on a surface of theprint carrier; applying on the surface of the print carrier a thin,homogenous fluid layer which fills the depressions with fluid; in astructuring process, generating ink-attracting and ink-repelling regionsso that the fluid in the depressions is substantially removed in theink-attracting regions and the fluid is not substantially removed in theink-repelling regions; applying on the surface ink that adheres in theink-attracting regions and does not adhere in the ink-repelling regions;and transferring to the carrier material the ink applied on the surfaceof the print carrier.
 40. A device to print a carrier material,comprising: a print carrier having a surface and depressions therein; anapplicator which applies a thin, homogenous fluid layer on the surfaceto fill the depressions with fluid; an image generator which generatesink-attracting and ink-repelling regions whereby the fluid in thedepressions is removed in the ink-attracting regions and the fluid isnot substantially removed in the ink-repelling regions; and an inkapplying station where ink that adheres in the ink-attracting regions onthe surface of the print carrier and does not adhere in ink-repellingregions is applied to the surface of the print carrier; an ink transferprinting station where ink applied on the surface of the ink carrier istransferred to the carrier material; and the applicator reapplies afluid layer on the same surface of the print carrier after the inktransfer.